What is a transit of Venus?
When Venus passes directly between earth and the sun, we see the distant planet as a small dot gliding slowly across the face of the sun. Historically, this rare alignment is how we measured the size of our solar system. The view is like a front row seat to the transit method, by which we now find planets around distant stars.
The 2012 transit of Venus, when the planet Venus appeared as a small, dark disk moving across the face of the Sun, began at 22:09 UTC on 5 June 2012, and finished at 04:49 UTC on 6 June. 
Depending on the position of the observer, the exact times varied by up to ±7 minutes. Transits of Venus are among the rarest of predictable celestial
phenomena and occur in pairs eight years apart: 
the previous transit was in June 2004, and the next pair of transits will not occur until December2117 and December 2125.
This image is taking from slooh.com to view transit of venus live online on Broome, Australia.